FBC memory devices are semiconductor memory devices expected recently as an alternative to 1T (Transistor)-1C (Capacitor) DRAM memories (JP-A2003-68877(KOKAI)). In the FBC (Floating Body Cell) memory device, an FET (Field Effect Transistor) with a floating body (hereinafter, also body) is formed on an SOI (Silicon On Insulator) substrate, and data “1” or data “0” is stored depending on the number of majority carriers accumulated in the body. FBCs are excellent in its compactness as compared to conventional DRAMs. To further increase the memory capacity of the FBC memory, its unit cell size needs to be further reduced. However, because of the limitation of manufacturing processes, further reduction of the cell size is not easy.
Meanwhile, in recent years, ferroelectric memories (FeRAMs (ferro-electric random access memories)) with a ferroelectric film are commanding attention as one type of non-volatile semiconductor memories (Non-Patent Document 1). To further increase the memory capacity of the ferroelectric memory, its unit cell size needs to be further reduced. However, also because of the limitation of manufacturing processes, further reduction of the cell size is not easy.